The folding mobile information terminal device in which two housings are coupled together by hinge portions and are constructed foldably is widely used. As the conventional device in which one housing is constructed to further turn in other directions in this folding mobile information terminal device, there is the device disclosed in JP-A-2001-251406, for example. The mobile information terminal device includes an inputting portion for inputting information, a displaying portion for monitoring an operation state and displaying received data, a controlling portion for controlling the inputting portion and the displaying portion, and a housing, wherein the inputting portion has a first inputting portion with numeric keys and a second inputting portion with function keys, the housing is divided in a first housing containing the second inputting portion and a second containing the displaying portion and the second inputting portion and both first and second housings are coupled together by hinge portions, and the first housing and the second housing are foldably and turnably coupled together by the hinge portions.
As the hinge mechanism for realizing such hinge portions, there is the mechanism disclosed in JP-A-2000-240636 and shown in FIGS. 22(A) and (B), for example. FIGS. 22(A) and (B) are a plan view and a side view of the hinge mechanism in the prior art. As shown in FIG. 22(A), the hinge portion is constructed to include an opening/closing shaft 202 supported turnably to an opening/closing shaft supporting portion 201, a turning shaft 203 rotatably passed through the opening/closing shaft 202 in their orthogonally intersecting state, an angle restricting piece 204 provided to come into contact with the opening/closing shaft supporting portion 201 and the opening/closing shaft 202 respectively, a restricting flange 205 provided to protrude from the turning shaft 203, and a turning restricting portion 206 fitted to the opening/closing shaft supporting portion 201 to face to the restricting flange 205. In the case where this hinge mechanism is applied to the above folding mobile information terminal device, as shown in FIG. 22(B), a size of the hinge portion formed by the turning shaft is decided by a distance R between a top end of the angle restricting piece 204, which is operated together with the turn of the turning shaft, and a center of the turning shaft.
Also, in JP-A-6-311216, the mobile phone in which a first housing composed of a first front housing and a first rear cover and a second housing composed of a second front housing and a second rear cover are turnably hinged together, a circular arc-like first curved-surface portion provided to an end portion of the first front housing and a circular arc-like second curved-surface portion provided to an end portion of the first rear cover are engaged with each other, an almost cylindrical first cavity portion that is communicated with an inside of the first housing is constructed at an end portion of the first housing and an almost cylindrical second cavity portion that is communicated with an inside of the second housing is constructed at an end portion of the second housing, the first cavity portion and the second cavity portion are arranged adjacently on the same shaft, and a flexible printed board for connecting an electric circuit in the first housing and an electric circuit in the second housing is wound helically along inner diameters of the first cavity portion and the second cavity portion to pass therethrough and also a cable provided to stretch over both housings is extended in a diameter of the helically-wound flexible printed board is disclosed.
However, when the conventional hinge mechanism is applied to the mobile phone having the above folding structure, an outer diameter of the hinge portion is enlarged to thus bring about an increase in size of the mobile phone. A size of the hinge portion is decided by a diameter of the opening/closing shaft and a radius of turn of the angle restricting piece provided to the end of the turning shaft. This radius of turn corresponds to the above distance R. Therefore, the configuration in which the angle restricting piece is provided to the end of the turning shaft brings out an increase of the radius of turn and as a result the hinge portion is increased in size. Also, since the mobile phone having the above folding structure has the structure that generates a bending stress and a torsional stress in the flexible printed board according to the folding operation, it is possible that conductor portions (circuit patterns) of the flexible printed board are disconnected. This problem will be explained concretely with reference to the drawing hereunder.
FIGS. 23(A) and (B) are a plan view of a flexible printed board through which a hinge portion in the prior art is passed. A flexible printed board 300 is wound and housed in the hinge portion to be connected to connectors that are provided to not-shown first and second housings respectively. In FIG. 23(A), in the case where the first and second housings are folded, one end of the board is indicated by a chain double-dashed line when the housings are folded until the state that a torsion angle P of the flexible printed board 300 that is wound clockwise from the lower side to the upper side is not changed.
However, since positions in which both ends of the flexible printed board 300 are fixed to the first and second housings (the lateral direction) are not changed, the torsion angle P is changed into an almost P/2 when the board is folded from the opened state. In other words, in this structure, the bending stress and the torsional stress are applied to the flexible printed board by the folding operation. Normally the flexible printed board has flexibility and has the enough strength to withstand the bending stress, but the disconnection or the breakage is caused if various stresses are applied compositely.
As a result, the mobile phone having the conventional folding structure is the structure that failures such as the disconnection or the breakage of the flexible printed board, etc. readily occur when the folding operation is repeated. Thus, there exists the problem such that the increase in size of the device is brought about or it is possible to cause the failures.